1. Field of the Invention
The present invention relates to a power steering system for vehicles which includes hydraulic reaction chambers for giving the vehicle operator a suitable reactive force or resistance to turning of the steering wheel.
2. Prior Art
There has heretofore been known a power steering system for vehicles which comprises a servo cylinder having a pair of hydraulic oil chambers, a four-way valve slidable in response to steering torque for selectively connecting the hydraulic oil chambers to a hydraulic pressure source and an oil reservoir, and a plurality of hydraulic reaction chambers disposed alongside of and substantially parallel to the valve and containing plungers and springs. The plungers are actuatable under hydraulic pressure in the hydraulic reaction chambers for limiting sliding movement of the four-way valve, thereby rendering steering torque that is necessary to variably rotate the steering wheel based on speeds of the vehicle and resistances from the road surface so as to enable the driver to feel a suitable resistance to turning of the steering wheel. The prior arrangement including the four-way valve and the reaction chambers has been relatively large in size because at least four reaction chambers are disposed circumferentially of the valve and the plungers in the reaction chambers are held between disk-shaped washers or thrust bearings mounted on the ends of the four-way valve.
Since the power steering system includes, in addition to the components described above, other attachments such as fluid conduits, a pump, and a gear box, a relatively wide space is required in the engine compartment of the vehicle. However, with the emission control apparatus being presently disposed in the engine compartment, the space available for a power steering system has become small. There has accordingly been a need for a smaller power steering system and hence smaller hydraulic reaction chambers. It has also been desired that the hydraulic reaction chambers be easily assembled and disassembled for easy maintenace and/or repair work in a limited space available in the engine compartment.